This invention relates to a four-cycle internal combustion engine crankcase ventilating system and more particularly to a crankcase ventilating system particularly adapted for use with four-cycle outboard motors.
The importance of ventilating the internal components of an internal combustion engine and particularly those associated with the crankcase chamber and the oil tank for the engine are well known. It has been the practice recently to employ so-called closed ventilating systems wherein the crankcase is ventilated primarily by the blowby gases that pass the piston rings during engine operation. In the interest of environmental concerns, these ventilating gases are then returned back to the combustion chamber for further combustion before they are discharged to the atmosphere. In this way, the emission of unburned hydrocarbons can be substantially reduced.
With conventional applications for four-cycle engines, the ventilation of the crankcase and the oil reservoir are not a significant problem. Outboard motors, however, provide a unique problem in connection with crankcase ventilation, on the other hand.
This is primarily because the engine is mounted in the power head of the outboard motor so that the crankshaft rotates about a vertically extending axis. This is in contradistinction to the normal disposition of this axis in a horizontal plane in most engine application.
Because of the vertical orientation of the crankshaft and, accordingly, the crankcase, the oil for the engine is normally maintained in a separate oil tank and the crankcase merely serves as a place to collect the oil and drain it or convey it to this separate oil tank. However, it is nevertheless important to treat the blowby gases and also to provide some crankcase ventilation. This presents significant problems with four-cycle outboard motors, particularly those having high outputs and utilizing overhead camshaft.
It is, therefore, a principal object of this invention to provide an improved crankcase ventilating system for a four-cycle outboard motor.
It is a further object of this invention to provide an improved crankcase ventilating system for a four-cycle engine that operates with its crankshaft rotating about the vertically extending axis, as is the practice with outboard motors.
Although crankcase ventilation is desirable, it also must be assured that the crankcase ventilating system does not function to deliver lubricating oil along the crankcase gases into the ventilating system and into the combustion chamber. Therefore, it is generally the practice to provide some form of separating mechanism for separating the oil from the ventilating gases. This is particularly important in connection with engines where the crankshaft rotates about a vertically extending axis since the draining system for returning the oil back to the separate oil reservoir becomes more complicated with such engine application.
It is, therefore, a still further object of this invention to provide an improved crankcase ventilating and oil separating arrangement for a four-cycle engine that has an output shaft rotating about a vertically extending axis.